The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Atomic layer deposition (ALD) may be used to deposit a monolayer of film on a substrate during each ALD cycle. During an ALD cycle, a surface of the substrate is exposed to a first precursor gas and provided with an externally supplied electrical bias voltage during a first period. The processing chamber is then evacuated and the substrate is exposed to a second precursor gas during a second period. The precursor gases react with the surface of the substrate in a self-limiting way. The reaction terminates once all the reactive sites on the surface are consumed.
ALD is a promising technology for future technology nodes since ALD controls thickness to the atomic level. However, there are some disadvantages with using ALD to deposit metals. For example, ALD of metal typically involves organic contaminants within the film, which reduces conductivity. There is also a lack of inherent selectivity between the metal and exposed dielectric film. Furthermore, precursor cost is relatively high.
Electroless deposition overcomes some of the disadvantages relating to selectivity, the quality of metal film and precursor cost. However, electroless deposition lacks atomic level thickness control, which is one of the key advantages of ALD. Additionally, it is challenging to deposit noble metals such as ruthenium (Ru) and platinum (Pt) using ALD.